2022 Fiscal Year Research-status Report
Effects of phyllosilicate minerals on fault slip of sandstone
| Project/Area Number |
22K14122
|
|---|
| Research Institution | Hiroshima University |
|---|
Principal Investigator |
|
|---|
| Project Period (FY) |
2022-04-01 – 2025-03-31
|
| Keywords | Fault slip behavior / Fault friction / Main Frontal Thrust / Himalayan Earthquakes / Rotary shear deformation / Creep behavior |
|---|
| Outline of Annual Research Achievements |
This research aims to elucidate the role of layered silicate minerals like chlorite, illite, and smectite on fault-slip behavior of sandstone from within the Himalayan Frontal Thrust Sheet. The study will provide insights on fault movement at shallow crustal depths (<10 km) from continental collisional zones (like Himalayas) as well as accretionary complexes (such as Japanese Islands), because sandstone is a major rock in both the continental collisional zones and accretionary complexes. Rotary shear apparatus installed at Kochi Core Center (JAMSTEC) was used for performing the deformation experiments at 15 MPa normal stress, 5 MPa pore water pressure, and creep to seismic slip velocities on the sandstone powders and gouges from the Nahan Thrust of the north-west Himalayas.
|
| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In the initial plan, dry experiments on gouge rocks were considered to be performed in the first stage. However, we have started the experiments with already natural conditions having 15 MPa normal stress and 5 MPa pore water pressure. In the first set of experiments we checked the reproducibility of the low velocity experiments at 10 μm/s, 100 μm/s, and 200 μm/s on two types of sandstone powders from the Nahan thrust. In second set of experiments we performed the velocity step experiments on the gouge samples of the Nahan Thrust under same conditions. We also performed the deformation experiments at seismic slip velocity (1.5 m/s) to obtain the slip weakening distance and specific fracture energy.
|
| Strategy for Future Research Activity |
In the present set of experiments we measured the mechanical properties of the sandstone and gouge powders at creep and seismic velocities. In the next stages the mineralogical variation will be measured by X-Ray Diffraction at Hiroshima University for the original and recovered samples (after the deformation experiments). Additionally, to extrapolate experimental results with the Himalayan fault, it is necessary to compare the microstructures formed in laboratory with the natural gouge samples. Although direct comparison is difficult as stress-strain and temperature paths are different for natural and laboratory samples. In the future set of experiments, the samples will be deformed at steady slip velocities to obtain microstructures representative at that slip velocity.
|
| Causes of Carryover |
In the 2022 fiscal year, one of the conferences could not be attended. Additionally there were restrictions in fieldwork travel, resulting in incurring amount to be used in fiscal year 2023. In fiscal year 2023, this amount will be used for fieldwork travel for further sample collection purposes. Additionally, the remaining amount will be used for travel expenses for conducting the experiments at Kochi Core Center.
|
